As set out in my U.S. Pat. No. 3,720,264, effective cleaning of openings in well liners can be done with liquid jets, provided that the jets have a velocity in excess of 700 feet per second and are directed at the liner from a standoff distance of less than 10 times the diameter of the jet orifice. Apparatus for accomplishing this effective cleaning method is described and claimed in U.S. Pat. No. 3,720,264 and divisionals thereof. Large-diameter casing in the 10- to 20-inch range, however, presents problems in easily obtaining the desired standoff distance with a single jet tool. This invention is directed to overcoming these problems.